Quickdraw, there's no reason to be rude.
I have some ideas about perhaps what it might have been, and I hope you don't snap at me too. Additionally, I'm very curious about why, after all these years, it bothers you.
It sounds to me that it might have been Alison Wonderland Syndrome, medically known as Todd's syndrome, which causes visual disturbances in children's brains. Probably caused by the aftermath of mono, which a child may not even realize they had.